Studies are being conducted to ascertain the mechanism of action of mammalian cytochrome c. These studies are focused on rates of electron transfer with non-physiological and physiological reductants and are designed to deduce the nature of the specific amino acid side chains participating in electron transfer. Of primary interest are the chemical and structural parameters that mediate the interaction of two macromolecules. Kinetics studies have to date allowed us to propose specific mechanisms. Our present work is focused on obtaining chemical and kinetic information which will prove or disprove our proposals. BIBLIOGRAPHIC REFERENCE: "Oxidation-Reductions Properties of Chromatium Vinosum High Potential Iron-Sulfur Protein" I.A. Mizrahi, F.E. Wood and M.A. Cusanovich, Biochem 15, 343 (1976).